LIS techniques are in contrast to open surgical techniques. They include operation through natural ducts within the body (endoscopy) and operation through one or more relatively small openings made by the surgeon in the patient's body (percutaneous techniques), for example laparoscopic surgery involving making small openings in the patient's abdominal wall, and arthroscopic surgery involving making small openings in a joint region. Advantages of LIS, compared to open surgery, are lower morbidity rates, shorter patient recovery times and lower costs of the procedure.
Surgical devices used in LIS are remotely operated. Typically devices are inserted into the patient's body, the operating head of the device is projected beyond the distal end of the housing, and this operating head is then activated by the surgeon from the proximal end of the device.
Simple, known LIS surgical devices use, for example, flexible steel wires which spring apart when extended from the distal end of a tube and which can be brought together again on withdrawal back into the tube. Examples of such devices are described, in U.S. Pat. Nos. 2,114,695, 2,137,710, 2,670,519, and 3,404,677.
Numerous LIS surgical devices incorporating a variety of special materials, including shape memory alloys are also known. U.S. Pat. No. 4,926,860 to Stice et al, issued 22 May 1990, for example, describes an arthroscopic procedure using a curved cannula and a normally straight shape memory alloy probe. The curved cannula facilitates access to parts of the joint, and bends the probe as it passes therethrough. However when the probe exits from the distal end of the cannula it adopts its normal straight configuration.
Also U.S. Pat No. 4,665,906 to Jervis discloses medical devices which make use of the pseudoelastic (SIM) properties of certain shape memory alloys. SIM pseudoelastic properties and their advantages are discussed in more detail later in this specification.
LIS devices incorporating elastic materials, including pseudoelastic shape memory alloys are also known, as described in U.S. Ser. No. 843,775 pending to the Applicant, filed Feb. 28, 1992. One embodiment described therein is an apparatus which enables passage of a ligature around a bone or other body member, or grasping of such a body member without requiring the surgical instrument to be swept over a wide angle of motion. The apparatus includes a cannula and a pseudo elastic member within the cannula. An example given is for the cannula to be straight and for the pseudo elastic member to adopt a curved configuration when extended from the cannula sufficient to grasp and manipulate a body structure. Another embodiment describes delivery of a needle to a surgical site through a curved arc by using a pseudo elastic needle. Other similar examples all involving the extension of pseudo elastic members from a housing to manipulate matter are described in U.S. Ser. No. 843,775. Other examples where the advantages of the pseudo elastic members in accessing difficult spaces within the patient's body would be evident to the man skilled in the art. The disclosure of U.S. Ser. No. 843,775 is incorporated herein by reference.
LIS surgical devices involving rotation of a knife are also known. For example, U.S. Pat. No. 4,723,545 to Nixon and Mombrimie, issued 9th Feb. 1988 describes a surgical instrument suited for arthroscopic surgery comprising a blade mounted in a tubular body portion so that it can project beyond the body portion and so that is can oscillate with respect to the body portion. This oscillation of the blade facilitates the cutting process, nothwithstanding the toughness or cut resistance of the tissue or the like which is to be repaired. Also U.S. Pat. No. 4203444 to Bonnell et al, issued on 20th May 1980 describes a surgical instrument for use in closed surgery of the knee, comprising an outer tube containing an inner tube. The inner tube is provided with shearing edges which form a blade. The inner tube can rotate within the outer tube at speeds in the range of 100-200 rpm, and a vacuum may be provided to withdraw the material sheared by the blade.
A problem experienced with the LIS and other surgical devices used in the past is in achieving movement in three dimensions to precisely access the desired surgical site, and to move the surgical instrument in the desired directions once it is at the desired surgical site.
U.S. Pat. No. 4882777 to Narula issued 21 Nov. 1989 provides some three dimensional character in the positioning of a catheter. This describes a catheter which is sufficiently resilient to deform to a linear configuration for insertion through a narrow tube, but which has a complex curvature that is not limited to a single plane. This skews the extreme distal end of the catheter relative to a straight portion and a first curved portion of the catheter, allowing automatic positioning of the distal end adjacent the desired internal location. However the automatic positioning is still to a desired predetermined position defined by the complex curvature of the catheter.
It is an object of the present invention to overcome the deficiencies of the prior art surgical devices, in particular the prior art LIS surgical devices.
It is a particular object of the present invention to provide a surgical device which allows another degree of freedom of movement to an operator of the surgical device, outside a single plane. In particular it is an object of the invention to provide a device in which the operator of the surgical device can deliver the head of the surgical device to a surgery site along a first path, which may be any direction of path but is typically a curved path in a single plane, and can then rotate the head of the device in another dimension, for example around the axis defined by the direction of the first path.
It is a further object of the present invention to provide a surgical device that is small in transverse dimensions, and is thus suitable for use in LIS techniques.